What is a fingerprint?

A fingerprint is an impression of the friction ridges on finger. Fingerprint ridges are formed during the third to fourth month of fetal development. The ridges begin to develop on the skin of the thumbs and fingers.The purpose of these ridges is to give the fingers a firmer grasp and to avoid slippage. These ridges allow the fingers to grasp and pick up objects.
The friction ridges on the fingers arrange themselves in more or less regular patterns with ridge characteristics. All fingerprints have a unique combination and arrangement of patterns and ridge characteristics.There are three main types of fingerprint; visible prints, latent prints, and impressed prints:

• Visible prints

Visible prints are also called patent prints and are left in some medium, like blood, that reveals them to the naked eye. They can be when blood, dirt, ink or grease on the finger come into contact with a smooth surface and leave a friction ridge impression that is visible without development.

• Latent prints

Latent prints are not apparent to the naked eye. They are formed from the sweat from sebaceous glands on the body or water, salt, amino acids and oils contained in sweat. The sweat and fluids create prints must be developed before they can be seen or photographed. They can be made sufficiently visible by dusting, fuming or chemical reagents.

• Impressed prints

Impressed prints are also called plastic prints and are indentations left in soft pliable surfaces, such as clay, wax, paint or another surface that will take the impression. They are visible and can be viewed or photographed without development.